Clarify language option default value behavior; NFC

The LANGOPT macro allows you to specify a default value for the
langauge option. However, it's expected that these values be constant
rather than depending on other language options (because the
constructor setting the default values does not know the language mode
at the time it's being constructed).

Some of our language options were abusing this and passing in other
language mode options which were then set correctly by other parts of
frontend initialization. This removes the default values for the
language options, and then ensures they're consistently set from the
same place when setting language standard defaults.

2 files changed, 10 insertions, 4 deletions

diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 7556dba..ba89b5a 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -7,7 +7,11 @@
 //===----------------------------------------------------------------------===//
 //
 // This file defines the language options. Users of this file must
-// define the LANGOPT macro to make use of this information.
+// define the LANGOPT macro to make use of this information. The arguments to
+// the macro are:
+//   LANGOPT(Name, Bits, DefaultValue, Description)
+// Note that the DefaultValue must be a constant value (literal or enumeration);
+// it cannot depend on the value of another language option.
 //
 // Optionally, the user may also define:
 //
@@ -107,7 +111,7 @@ LANGOPT(Trigraphs         , 1, 0,"trigraphs")
 LANGOPT(LineComment       , 1, 0, "'//' comments")
 LANGOPT(Bool              , 1, 0, "bool, true, and false keywords")
 LANGOPT(Half              , 1, 0, "half keyword")
-LANGOPT(WChar             , 1, CPlusPlus, "wchar_t keyword")
+LANGOPT(WChar             , 1, 0, "wchar_t keyword")
 LANGOPT(Char8             , 1, 0, "char8_t keyword")
 LANGOPT(IEEE128           , 1, 0, "__ieee128 keyword")
 LANGOPT(DeclSpecKeyword   , 1, 0, "__declspec keyword")
@@ -116,9 +120,9 @@ BENIGN_LANGOPT(AsmPreprocessor, 1, 0, "preprocessor in asm mode")
 LANGOPT(GNUMode           , 1, 1, "GNU extensions")
 LANGOPT(GNUKeywords       , 1, 1, "GNU keywords")
 VALUE_LANGOPT(GNUCVersion , 32, 0, "GNU C compatibility version")
-BENIGN_LANGOPT(ImplicitInt, 1, !C99 && !CPlusPlus, "C89 implicit 'int'")
+BENIGN_LANGOPT(ImplicitInt, 1, 0, "C89 implicit 'int'")
 LANGOPT(Digraphs          , 1, 0, "digraphs")
-BENIGN_LANGOPT(HexFloats  , 1, C99, "C99 hexadecimal float constants")
+BENIGN_LANGOPT(HexFloats  , 1, 0, "C99 hexadecimal float constants")
 LANGOPT(CXXOperatorNames  , 1, 0, "C++ operator name keywords")
 LANGOPT(AppleKext         , 1, 0, "Apple kext support")
 BENIGN_LANGOPT(PascalStrings, 1, 0, "Pascal string support")
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index f586f8d..83de27b 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3263,6 +3263,8 @@ void CompilerInvocation::setLangDefaults(LangOptions &Opts, InputKind IK,
   Opts.GNUCVersion = 0;
   Opts.HexFloats = Std.hasHexFloats();
   Opts.ImplicitInt = Std.hasImplicitInt();
+  Opts.WChar = Std.isCPlusPlus();
+  Opts.Digraphs = Std.hasDigraphs();
 
   Opts.HLSL = IK.getLanguage() == Language::HLSL;